DigiTemp v3.1.0 Frequently Asked Questions
Copyright 2003 by Brian C. Lane <bcl@brianlane.com> www.brianlane.com

Q. Where Do I buy Parts?

   For those who want a pre-assembled sensor I am selling DS18S20 sensors
   on a 6" piece of phone cable. It includes a modular connector and an
   optional 1N5817 diode (for clamping ringing on long wire runs).
   The basic DigiTemp kit with adapter and 2 sensors is $35 + shipping.
   See the DigiTemp hardware page at http://www.brianlane.com/dthardware.php

   I now have a PC board based sensor with 2 RJ-45 connectors, a diode to 
   clamp network ringing, and jumpers to select passive sensors or +5v
   powered sensors.

   If you want to build them yourself you can get parts from:

   www.ibutton.com sells the DS9097U-009, as does Dallas/Maxim. Their lead
   times are long and inconsistent, so if you need one quickly you should
   contact me to see if I have any in stock. Another source is AAG at
   www.aag.com.mx, they also make 1-wire weather stations and rain gauge
   adapter kits.

   I order my temperature sensors directly from Dallas Semiconductor
   at 1-800-336-6933 (http://www.dalsemi.com/sales/credit_card.html)

   DigiKey (http://www.digikey.com) now has DS18S20 sensors in stock as
   well.

Q. How do I connect it to the RJ-11 of the DS9097-U

   Take a look at the DS9097-U data sheet at
     http://pdfserv.maxim-ic.com/arpdf/DS9097U-009-DS9097U-S09.pdf

   Ground is the pin on the right and data is the pin on the left (using
   the two center pins of the RJ-11).

   Even with this information you will probably get it backwards the first
   time so make a temporary connecting the first time and confirm that 
   you have the correct polarity.

   Holding the RJ-11 plug so that it is facing you (as if you were going to
   plug it into your mouth), with the clip on the top.
             ____
           --|  |--
           | 4321 |
           --------

   1 = NC
   2 = Ground
   3 = Data
   4 = NC
   


Q. How many can I connect?

   Read the Dallas Semiconductor Tech. Brief on the One Wire Network.
     http://www.maxim-ic.com/appnotes.cfm/appnote_number/570
   It covers everything you want to know and more. The limit comes down to
   wiring, how much you have and how good it is. Other than that you can
   connect as many as you need.

   www.pointsix.com also has some very good app notes on network length
   and ringing problems.

Q. How long can the wire be?

   Again, read the Tech. Brief above. This depends on the cable. Using
   better cable will allow you to extend the cable longer distances.

Q. I have glitches in my data, what do I do?

   The first solution is to check all of your connections to make sure
   they are soldered or well connected.
   Next, is your cable decent quality? Cat-5 is the best, with twisted
   telephone cable coming in second.
   If you are still having problems you should try Using a Schottky
   diode across the cable's end. Connect the diode reverse-biased with
   the cathode (the stripe) on the data line and anode on the return. 

   I used a 1N5818 across my attic sensor -- before adding this I was
   getting multiple glitches per hour. Now I have seen 1 glitch in
   about 2 weeks. 

   You can also buy pre-assembled sensors that include a 1N5817 diode from
   my DigiTemp Hardware page at http://www.brianlane.com/dthardware.php

Q. What is the difference between the DS9097-U and the App. Note 74 type
   of adapter.

   The DS9097-U adapter uses a serial port to 1-wire conversion chip that
   makes talking to the 1-wire network easier. DigiTemp v2.x uses this
   type of adapter (the DS9097U-009 and -S09 both work fine).

   The old style of adapter (sometimes called passive or App. Note #74)
   used only diodes and resistors to convert the serial port voltages to
   the one-wire voltages. Dallas still sells adapters of this type, part
   number DS9097 and DS9097E that is built on this design. DigiTemp v1.x
   supports this type of adapter, and include a HOWTO document with
   instructions for building your own.

   As of DigiTemp v3.0.0 support for both style adapters has been integrated
   into the same code tree. You no longer need to use v1.x for the DS9097 passive
   adapter and v2.x for the DS9097U adapter.

Q. When will digitemp support the one-wire hub?

   It does! As of v2.3 it scand for the DS2409 couplers used in the hubs
   and keeps track of which branch it finds the sensors on. It doesn't
   support cascaded hubs (hubs connected behind a hub), only multiple hubs
   on the main 1-wire lan.
   
Q. When will Digitemp support the one-wire Weather Station?

   Probably never. DigiTemp has 1 purpose - to read temperatures. Weather
   station support is more complicated and requires a dedicated program to
   be watching the station and recording events like weather vane movement
   and wind-speed calculations. I may add support for humidity and
   barometric pressure, especially if someone were to donate a unit for me
   to use.

   I have found a possible source for Humidity, Barometer and Lightning 
   sensors at http://www.jjware.com/index2.htm
   
   I do have plans to write my own weather station software though. No release
   date as of yet, but it is being worked on.
